Gray

"We were the next generation of a project launched in Roswell. We were to be unstoppable ground troops, unfazed by cold or radiation. In other cases, our DNA was to be harvested to create biomodifications for humans, so that they could survive the aftermath of a nuclear war.

To prevent us from overpowering our masters by sheer numbers, we were created unable to reproduce. That is why the Templar threat to us is so dire — we are all that remains.
"

Grays are the products of experiments undertaken by Majestic 12 at Area 51. These experiments were collectively known as the 'bovine manipulation project', which was underway by at least 2029, as evidenced by messages on the VersaLife corporate vault computer. The grays are created by crossing DNA retrieved from various different creatures (most likely including monkeys); hence grays, along with greasels and karkians, are known as transgenics. When the bovine manipulation project was first undertaken, the gray lifeforms were viewed as a failure. However, the idea to use them to protect MJ12 facilities was put forward by Bob Page to the Illuminati leader, Lucius DeBeers. It is unclear if the Illuminati supported Page's idea while he was still a member of the organization. Either way, by 2052, grays were being used to guard top secret MJ12 facilities.

Grays have a silvery-gray complexion and are hairless. They have enlarged heads, solid black eyes, and long, gangling arms and legs. Their appearance closely resembles the stereotypical depiction of the supposed Roswell aliens. In fact, those working for MJ12 non-directly believe that they actually are aliens, likely retrieved from the Roswell Crash, however this is likely false information meant to discredit anyone who defects from MJ12 and attempts to expose their activities.

Grays thrive in frigid or radioactive environments (but are capable of living in warm and non-radioactive environments as well), hence the reason why they are normally found in radioactive areas in Area 51, and why they live in Antarctica in Deus Ex: Invisible War.

Grays can swipe at enemies as a melee attack. Their ranged attacks consist of bursts of radiation.

Grays in Deus Ex do not talk, because in the only two areas where they are found (VersaLife HQ and Area 51), they are kept isolated in cages and have thus become feral and hostile. During the Collapse, JC Denton frees the grays from Area 51, and convinces them to help him. It is unclear how the grays became more civilized (JC's merger with Helios may be a factor), but in Deus Ex: Invisible War, not only do the grays talk but they are also very friendly to any ally of ApostleCorp. The grays are also revealed to live in Antarctica. Due to their lack of biomod infusions, grays cannot go through the portal, and so must be transported the long way to the ApostleCorp facility in Trier.

Grays will readily attack any enemy of ApostleCorp, including the player (Alex Denton), if he/she is affiliated with another faction in the endgame. Because grays are genetically-engineered, the Knights Templar attempt to kill them whenever possible. In the Templar ending, a gray can be seen hanging from a noose.